Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies

Plasma Physics and Controlled Fusion IOP Publishing 66:2 (2024) 025005

Authors:

RW Paddock, TS Li, E Kim, JJ Lee, H Martin, RT Ruskov, S Hughes, SJ Rose, CD Murphy, RHH Scott, R Bingham, W Garbett, VV Elisseev, BM Haines, AB Zylstra, EM Campbell, CA Thomas, T Goffrey, TD Arber, R Aboushelbaya, MW Von der Leyen, RHW Wang, AA James, I Ouatu, R Timmis, S Howard, E Atonga, PA Norreys

Energy gain of wetted-foam implosions with auxiliary heating for inertial fusion studies

Plasma Physics and Controlled Fusion IOP Publishing 66:2 (2023) 025005

Authors:

Robert W Paddock, Tat S Li, Eugene Kim, Jordan J Lee, Heath Martin, Rusko T Ruskov, Stephen Hughes, Steven J Rose, Christopher D Murphy, Robbie HH Scott, Robert Bingham, Warren Garbett, Vadim V Elisseev, Brian M Haines, Alex B Zlystra, E Mike Campbell, Cliff A Thomas, Tom Goffrey, Tony D Arber, Ramy Aboushelbaya, Marko W Von der Leyen, Robin HW Wang, Abigail A James, Iustin Ouatu, Robin Timmis

Abstract:

Low convergence ratio implosions (where wetted-foam layers are used to limit capsule convergence, achieving improved robustness to instability growth) and auxiliary heating (where electron beams are used to provide collisionless heating of a hotspot) are two promising techniques that are being explored for inertial fusion energy applications. In this paper, a new analytic study is presented to understand and predict the performance of these implosions. Firstly, conventional gain models are adapted to produce gain curves for fixed convergence ratios, which are shown to well-describe previously simulated results. Secondly, auxiliary heating is demonstrated to be well understood and interpreted through the burn-up fraction of the deuterium-tritium fuel, with the gradient of burn-up with respect to burn-averaged temperature shown to provide good qualitative predictions of the effectiveness of this technique for a given implosion. Simulations of auxiliary heating for a range of implosions are presented in support of this and demonstrate that this heating can have significant benefit for high gain implosions, being most effective when the burn-averaged temperature is between 5 and 20 keV.

Observation of monoenergetic electrons from two-pulse ionization injection in quasilinear laser-wakefields

Physical Review Letters American Physical Society 130 (2023) 105002

Authors:

Marko von der Leyen, James Holloway, Y Ma, Pt Campbell, Ramy Aboushelbaya, Q Qian, Af Antoine, M Balcazar, J Cardarelli, Qingsong Feng, R Fitzgarrald, Bx Hou, G Kalinchenko, J Latham, Am Maksimchuk, A McKelvey, J Nees, Iustin Ouatu, Robert Paddock, Benjamin Spiers, Agr Thomas, Robin Timmis, Karl Krushelnick, Peter Norreys

Abstract:

The generation of low emittance electron beams from laser-driven wakefields is crucial for the development of compact X-ray sources. Here, we show new results for the injection and acceleration of quasi-monoenergetic electron beams in low amplitude wakefields experimentally and using simulations. This is achieved by using two laser pulses decoupling the wakefield generation from the electron trapping via ionization injection. The injection duration, which affects the beam charge and energy spread, is found to be tunable by adjusting the relative pulse delay. By changing the polarization of the injector pulse, reducing the ionization volume, the electron spectra of the accelerated electron bunches are improved.

Measuring the principal Hugoniot of ICF-relevant TMPTA plastic foams

Physical Review E: Statistical, Nonlinear, and Soft Matter Physics American Physical Society 107 (2023) 025206

Authors:

Robert Paddock, Marko von der Leyen, Ramy Aboushelbaya, Peter Norreys, David Chapman, Daniel Eakins

Abstract:

Wetted-foam layers are of significant interest for inertial confinement fusion capsules, due to the control they provide over the convergence ratio of the implosion, and the opportunity this affords to minimize hydrodynamic instability growth. However, the equation of state (EOS) for fusion relevant foams is not well characterized, and many simulations rely on modelling such foams as a homogeneous medium with the foam average density. To address this question, an experiment was performed using the the VULCAN Nd:glass laser at the Central Laser Facility. The aim was to measure the principal Hugoniot of TMPTA plastic foams at 260 mg/cm3 , corresponding to the density of liquid DT-wetted-foam layers, and their ‘hydrodynamic equivalent’ capsules. A VISAR was used to obtain the shock velocity of both the foam and an α-quartz reference layer, while streaked optical pyrometry provided the temperature of the shocked material. The measurements confirm that, for the pressure range accessed, this material can indeed be well described using the equation of state of the homogeneous medium at the foam density.

Measuring the principal Hugoniot of inertial-confinement-fusion-relevant TMPTA plastic foams

Physical Review E American Physical Society 107:2 (2023) 25206

Authors:

Robert W Paddock, Marko W von der Leyen, Ramy Aboushelbaya, Peter A Norreys, David J Chapman, Daniel E Eakins, M Oliver, RJ Clarke, M Notley, CD Baird, N Booth, C Spindloe, D Haddock, S Irving, RHH Scott, J Pasley, M Cipriani, F Consoli, B Albertazzi, M Koenig, AS Martynenko, L Wegert, P Neumayer, P Tchórz, P Rączka

Abstract:

Wetted-foam layers are of significant interest for inertial-confinement-fusion capsules, due to the control they provide over the convergence ratio of the implosion and the opportunity this affords to minimize hydrodynamic instability growth. However, the equation of state for fusion-relevant foams are not well characterized, and many simulations rely on modeling such foams as a homogeneous medium with the foam average density. To address this issue, an experiment was performed using the VULCAN Nd:glass laser at the Central Laser Facility. The aim was to measure the principal Hugoniot of TMPTA plastic foams at 260 mg/cm3, corresponding to the density of liquid DT-wetted-foam layers, and their “hydrodynamic equivalent” capsules. A VISAR was used to obtain the shock velocity of both the foam and an α-quartz reference layer, while streaked optical pyrometry provided the temperature of the shocked material. The measurements confirm that, for the 20–120 GPa pressure range accessed, this material can indeed be well described using the equation of state of the homogeneous medium at the foam density.